<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 扩大边框法 */
        .button1{
            width: 100px;
            height: 100px;
            border-radius: 50%;
            background-color: bisque;
            cursor: pointer;

            /* 扩大20px的可选范围 */
            border: 20px solid transparent;
            background-clip: padding-box;

            /* 用box-shadow来模拟边框 */
            box-shadow: 0 0 0 1px black inset;
        }

        /* 伪元素法 */
        .button2{
            width: 100px;
            height: 100px;
            border-radius: 50%;
            background-color: bisque;
            cursor: pointer;
            border: 1px solid black;
            position: relative;
        }
        /* 伪元素可以代表宿主元素来响应鼠标交互 */
        .button2:before{
            content: '';
            position: absolute;
            /* 伪元素法可以放在任何地方 */
            top: -10%;
            right: -10%;
            width: 120%;
            height: 120%;
            border-radius: 50%;
            border: 1px solid red;
        }


    </style>
</head>
<body>
    <div class="button1"></div>
    <div class="button2"></div>
</body>
</html>